Bump cryptography from 2.6.1 to 2.7
Bump cryptography from 2.6.1 to 2.7

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.6.1 to 2.7.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pyca/cryptography/compare/2.6.1...2.7)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
DemocracyClub/yournextrepresentative,DemocracyClub/yournextrepresentative,DemocracyClub/yournextrepresentative